Device and process for joining fitting parts on hollow profiles by means of fluid high internal pressure

ABSTRACT

A device and method for joining fitting parts provided with a passage opening on hollow profiles through partial expansion of the hollow profiles at the location of the fitting parts is provided. The fitting parts are slid on with the passage openings and are held in position by means of fluid high internal pressure expansion of the hollow profile. The device includes an expanding lance, which can be slid into the hollow profile and exhibits an axial borehole for the purpose of guiding the pressure fluid. The axial borehole is connected to a fluid high pressure generating system and exhibits a cross channel with an outlet for the pressure fluid in the direction of the hollow profile location to be expanded. The shell surface of the expanding lance exhibits sealing elements that are spaced apart and that define the outlet so as to seal axially on both sides against high pressure. To a reliable joining of the fitting parts on hollow profiles even when the hollow profiles exhibit small outer diameters, it is proposed that the expanding lance comprises two separate, aligned oblong components, of which at least one bears the axial borehole which empties freely on an end face near the outlet. The facing ends of the lance components form the cross channel for the axial borehole of the expanding lance. Furthermore, the device includes a drive unit operable to drive the two lance components into respective hollow profile ends, and are supported on an end side during the expansion phase.

BACKGROUND OF THE INVENTION

[0001] This application claims the priority of German Patent Document199 57 508.8, filed in Germany, Nov. 30, 1999, the disclosure of whichis expressly incorporated by reference herein.

[0002] The invention relates to a device and process for joining fittingparts on hollow profiles fluid high internal pressure.

[0003] A device of this general type is known from German PatentDocument 37 16 986 A1 (corresponding to U.S. Pat. No. 5,054,756). Thehollow profile is expanded plastically at the joining location by meansof fluid high internal pressure. The more solid fitting part is expandedsimultaneously within the elastic limits. Following high pressurerelease, the fitting part springs back at the internal diameter of itspassage opening, whereas the hollow profile remains in its plasticizedstate. These physical features make it possible to achieve a very high,virtually undetachable press-fit joint between the fitting part and thehollow profile. In operation, i.e., at an existing high internalpressure, the expanding lance, which is used for this purpose anddescribed there, is highly subjected to extreme tensile stress so thatconstructive measures, such as for example an increase in the ratio ofthe lance diameter to the diameter of the axial borehole, which runs inthe expanding lance and guides the pressure fluid, must be taken inorder to prevent the expanding lance from tearing and to guarantee inthis manner a reliable process for joining the fitting parts on thehollow profiles. Nevertheless, the lance is subject to relatively highwear due to the high tensile stress or the mechanical stress alternatingbetween stress and relief in the course of the operating life of theexpanding lance. For this reason after a specific period of use it isnecessary to repair the lance or make an expensive replacement with anidentical new lance. Furthermore, hollow profiles with a small outerdiameter, i.e., less than 16 mm, cannot be reliably joined by thecustomary method, since in the course of the process the use ofcorrespondingly thin (less than 10 mm outer diameter) expanding lancesresults in the lance snapping after just a few expansion operations(called “shots” in the technical jargon due to their speed). This statein turn results inevitably in a production standstill and a rejectedpart.

[0004] An object of the invention is to improve a device of this classto the effect that the joining of fitting parts on hollow profiles bymeans of partial high internal pressure deformation is also possible andreliable with an expanding lance even when the hollow profiles exhibitsmall outer diameters.

[0005] This object is achieved by the invention by providing a devicefor joining fitting parts, provided with a device for joining fittingparts, provided with a passage opening, on a hollow profile throughpartial expansion of the hollow profile at a location of the fittingparts, slid on with the passage opening, by means of fluid high internalpressure, said device comprising an expanding lance, which can be slidinto the hollow profile and exhibits an axial borehole for the purposeof guiding the pressure fluid, said axial borehole being connected,first of all, to a fluid high pressure generating system and secondlyexhibiting a cross channel with an outlet for the pressure fluid in adirection of the hollow profile location to be expanded, whereby theshell surface of the expanding lance exhibits sealing elements that arespaced apart and that define an outlet so as to seal axially on bothsides against high pressure, wherein the expanding lance comprises twoseparate, aligned components, of which at least one bears the axialborehole, which axial borehole empties freely on an end face near anoutlet of said at least one component, end faces of the oblongcomponents that face each other forming a cross channel for the axialborehole of the expanding lance, and wherein the device includes a driveunit, operable to drive the two components into the hollow profile end,facing the respective component, and are supported on the end sideduring the expansion phase.

[0006] Thanks to the invention, tensile stress of the expanding lance isavoided. The two components of the lance are subjected only to pressureso that the lance is prevented from tearing. Since the stability of thelance with respect to an adequately strong “wall thickness” is no longerimportant due to the solution of the invention, the outer diameter ofthe expanding lance and the axial borehole can be dimensioned very smalland, nevertheless, work reliably. In this manner fitting parts can alsobe joined in the desired manner on hollow profiles with small outerdiameter by means of partial high internal pressure deformation with thepressure fluid-guiding expanding lance.

[0007] With the device of the invention, joining is done preferablysequentially. This means that each individual joint along the hollowprofile is approached in succession by displacing the expanding lanceinside the hollow profile. For few fitting parts this type of joiningdoes exhibit negligibly higher timing than the joining of parts in ashot. Furthermore, it has been demonstrated to be advantageous for theprocess if owing to the small volume of fluid, required for sequentialjoining, the time for building up the high fluid pressure is also veryshort. Furthermore, the assembly of the expanding lance is significantlysimplified over the conventional one.

[0008] Hence, it is not necessary to have a leakage borehole fordraining the fluid volume from the hollow profile in the direction ofthe outside. Said volume of fluid creeps past the sealing arrangement,sealing both sides of the expansion point in the axial direction, andinto the pressure-free, adjoining annular slit. Or when the previousseal fails, there is the risk of an expansion between the fitting parts,since in the case of a leak, the pressure fluid—when the seal carrierfor passage of an adequately large quantity of fluid volume has beensuitably designed—can flow out unimpeded.

[0009] In addition, objects achieved in this respect by means of theinvention are that the design of the high pressure unit can be simpler,since it is no longer necessary that it automatically recognize a dropin pressure. In addition, there is no need for spacer sleeves andpositioning stops. Furthermore, it is significantly simpler tocompensate for the manufacturing-induced concentricity error at theinternal diameter of the hollow profile with the design of the expandinglance, since only the single expansion area of the expanding lance mustbe designed in accordance with the error tolerance. This featurecontributes to the simplified design of the expanding lance and to theuse of less precisely machined and, therefore, less expensive hollowprofiles.

[0010] Another important advantage of the expanding lance having twoparts is that the two components can be spaced axially apart at variabledistances so that with only one sealing arrangement at the hollowprofile, expansions of varying length can be formed. Furthermore, thereis the possibility of tailoring individually the fluid pressure heightto the diverse expansion points and their desired final shape.

[0011] It is also contemplated by the invention to provide one or bothcomponents of the lance with other cross boreholes so that severalpoints on the hollow profile can be expanded—as usual—simultaneously inone shot. In so doing, the customary lance head can be dispensed with.However, the aforementioned advantages of sequential joining also dropaway.

[0012] Advantageous designs of the invention are disclosed below and inthe claims.

[0013] Other objects, advantages and novel features of the presentinvention will become apparent from the following detailed descriptionof the invention when considered in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The single drawing FIGURE is a sectional view of a device forjoining fitting parts, constructed according to a preferred embodimentof the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0015] The single drawing FIGURE depicts a device 1 for joining fittingparts, for example cams 3 and 4, provided with a passage opening 2, onhollow profiles, for example a hollow shaft 5, in order to form acamshaft. Said device works with fluid high internal pressure and bringsabout through partial expansion of the hollow shaft 5 at the location ofthe cams 3 and 4, which are slid on with the passage opening 2, thejoining that ends in a very strong press-fit joint.

[0016] The device 1 includes an expanding lance 6, which is slid intothe hollow shaft 5 and comprises two separate, aligned oblong components7 and 8. In both components 7, 8 there runs centrally an axial borehole9, in which the pressure fluid is guided and which exhibits an inlet 10at the longer component 7. The inlet 10 is connected to a fluid highpressure generating system and is located outside the hollow shaft 5, tobe joined when both components 7, 8 are slid into the hollow shaft 5.Furthermore, the axial borehole 9 exhibits in the outward direction onthe shorter hollow shaft 8 an outlet 11, which is also located outsidethe hollow shaft 5 to be joined when both components 7, 8 are in theslide-in position in the hollow shaft 5. The described arrangement ofthe inlet 10 and the outlet 11 makes it possible to fill quickly andwithout air bubbles the expanding lance 6 and the annular expansionspace 12 with pressure fluid at the point on the hollow shaft 5 to beexpanded. The outlet 11 exhibits a check valve 13, which is closedduring expansion in order to build up pressure and is opened followingexpansion for fast pressure relief.

[0017] As an alternative, the axial borehole 9 can also run only in thecomponent 7. In this case, it must also exhibit, in addition to theinlet 10, the outlet 11. In this respect the component 8 does notexhibit any borehole and is, therefore, simpler to produce. It is alsoconceivable according to the invention that both components 7 and 8exhibit one outlet 11 and one inlet 10 each and thus the component 8 canalso be connected to a fluid high pressure generating system. Thus, thefilling with pressure fluid and pressure relief can be especially fast.

[0018] The device 1 can include a pressure reservoir, which isintercalated with respect to fluid flow between the fluid high pressuregenerating system and the inlet 10 of the axial borehole 9 The pressurereservoir balances the pressure fluctuations of the fluid high pressuregenerating system so that the degree of expansion can be set with highprecision. In addition, the reliability of the process can be furtherimproved since there are no longer any pressure peaks that damage thehollow shaft. Furthermore, the pressure reservoir in the said embodimentwith two inlets—one in each component 7, 8—can be connected to bothinlets. In this manner there is uniform pressure in the expanding lance6 without the expense of synchronization.

[0019] In the embodiment depicted in the drawing, the axial borehole 9empties into the faces 14, 15 of the components 7, 8 that face eachother. The faces 14, 15 can lie side-by-side, as in the case of joiningthe narrower cam 3, or also be spaced apart, as in the case of joiningthe thicker cam 4. The distance depends in essence on the axial reach ofthe necessary expansion. When the faces 14, 15 lie side-by-side, as inthe case of the hollow shaft 5 being expanded at the location of thenarrower cam 3, the exact positioning of the expanding lance 6 at theexpansion point of the hollow shaft is relatively simple owing to thecomplementary stop, which belongs to the components 7, 8 and is formedby the faces 14, 15. Somewhat more complicated is the positioning of theindividual components 7, 8 when the spacing between the faces is greaterduring the joining operation of the cam 4, since each component 7, 8 hasto be assigned a positioning device, such as, for example, a positionmeasuring sensor.

[0020] In each case the faces 14, 15 form together a cross channel 16for the axial borehole 9, which empties freely into these two components7, 8 on the faces 14, 15. The cross channel 16 leads in the direction ofthe expanding location into the annular expansion space 12, which isformed by the radial distance of the expanding lance from the insidewall 17 of the hollow shaft 5 and where said cross channel exhibits anoutlet 18. Set back axially from the faces 14, 15, the components 7, 8of the expanding lance 6 exhibit on the shell surface 22 collar-likesupport shoulders 19, 20, against which rests a sealing element, whichis formed preferably by an elastic ring seal 21, on the side, facing thecross channel. The ring seals 21 define axially on both sides theexpansion space 12 and seal it and thus also the outlet 18 of the crosschannel 16 against the high pressure. The support shoulders 19, 20 arelocated in the hollow shaft 5 with almost no gap in the direction of theinside wall 17 in order to avoid an extrusion of the ring seals 21 andthus irreparable damage due to stress from the high internal pressure.

[0021] Within a short distance from the expanding location, the device 1exhibits supports 23, 24, by means of which the two components 7, 8 areheld immoveably in the radial direction. Thus, the components 7, 8cannot buckle. The support 23 is arranged on component 8 outside thehollow shaft 5 and is formed by a steady rest, which reaches around thecomponent 8 on the peripheral side. The component 7 bears a slid-onguide sleeve, which forms the support 24 and is arranged inside thehollow shaft 5. This guide sleeve rests on the outside against theinside wall 17 of the hollow shaft 5 and experiences by means of thesame the necessary support force.

[0022] For the purpose of joining the fitting parts, the device 1 worksas follows. First, the cams 3 and 4 are slid with their passage opening2 onto the hollow shaft 5 to the desired position. Then the components 7and 8 are slid into the respective hollow shaft end 25, 26 and placed insuch a manner at the site of the slid-on cams 3, 4 that the faces 14, 15come to rest in such a manner relative to each other that the expansionspace 12 extends exactly over the length of the passage opening 2 of thecams 3 and 4. The axial distance between both faces 14, 15 is relativelyshort with respect to the cam 3 and very wide with respect to the cam 4.

[0023] For the purpose of sliding in the components 7, 8, the device 1exhibits for each component 7, 8 a drive unit 27, which is formed by ahydraulic cylinder. The hydraulic cylinder exhibits a receptacle 28 forone end 29 of one of the components 7, 8 of the expanding lance 6. Bymeans of the hydraulic cylinder, the two components 7, 8 are driven intothe hollow profile end 25, 26, facing the same. The hydraulic cylindersremain in their extended position after the components 7, 8 have reachedtheir expansion position. The expansion space 12 is now filled withpressure fluid over the axial borehole 9 and the cross channel 16 of theexpanding lance 6. Thereafter, the check valve 13 is closed.

[0024] At this point the fluid high pressure generating system generatesa fluid high pressure, whereby the hollow shaft 5 expands plastically atthis point of the expansion space 12 due to being subjected to thepressure fluid. At the same time the cam 3 expands elastically over theexpansion of the hollow shaft 5. During the expansion phase thecomponents 7, 8 are supported on one end by means of the hydrauliccylinder. In generating the fluid high pressure, the ring seals 21 arepressed against the support shoulders and spread apart radially. In thismanner a very high contact force against the inside wall 17 of thehollow shaft 5 is attained that guarantees a high pressure-tight seal.

[0025] Following expansion, the check valve 13 and thereby the outlet 11are opened and the pressure fluid is thus relieved. Owing to the relief,the cam 3 on its wall defining the passage opening 2 springs back in thedirection of the hollow shaft 5, which remains in its expanded positiondue to the plasticizing. In this manner a very strong press-fit joint isproduced. The two components 7, 8 are now moved to the location of thesecond expansion, thus to the location of the cam 4, in the same manneras described for the cam 3, by means of the hydraulic cylinder.Thereafter the cam 4 can be joined.

1. Device for joining fitting parts, provided with a passage opening, ona hollow profile through partial expansion of the hollow profiles at thelocation of the fitting parts, slid on with the passage opening, bymeans of fluid high internal pressure, said device comprising anexpanding lance, which can be slid into the hollow profile and exhibitsan axial borehole for the purpose of guiding the pressure fluid, saidaxial borehole being connected, first of all, to a fluid high pressuregenerating system and secondly exhibiting a cross channel with an outletfor the pressure fluid in a direction of the hollow profile location tobe expanded, whereby the shell surface of the expanding lance exhibitssealing elements that are spaced apart and that define an outlet so asto seal axially on both sides against high pressure, wherein theexpanding lance comprises two separate, aligned components, of which atleast one bears the axial borehole, which axial borehole empties freelyon an end face near an outlet of said at least one component, end facesof the oblong components that face each other forming a cross channelfor the axial borehole of the expanding lance, and wherein the deviceincludes a drive unit, operable to drive the two components into thehollow profile end, facing the respective component, and are supportedon the end side during the expansion phase.
 2. Device as claimed inclaim 1, wherein that the drive unit is an hydraulic cylinder with areceptacle for one end of one of the components of the expanding lance.3. Device as claimed in claim 1, wherein the axial borehole extends inboth components, whereby the axial borehole of each component exhibitsin an outward direction one of an inlet and an outlet that is disposedoutside the hollow profile to be joined when both components are slidinto the hollow profile.
 4. Device as claimed in any one of the claim 2,wherein the axial borehole extends in both components, whereby the axialborehole of each component exhibits in an outward direction one of aninlet and an outlet that is disposed outside the hollow profile to bejoined when both components are slid into the hollow profile.
 5. Deviceas claimed in claim 3, wherein that the outlet is connected to a checkvalve which closes said outlet when the hollow profile is subjected tothe high internal pressure and opens the same after an expansion phase.6. Device as claimed in claim 4, wherein that the outlet is connected toa check valve which closes said outlet when the hollow profile issubjected to the high internal pressure and opens the same after anexpansion phase.
 7. Device as claimed in claim 1, wherein the deviceincludes a pressure reservoir which is connected, on the one hand, to afluid high pressure generating system and, on the other hand, to fluidflow to the axial borehole.
 8. Device as claimed in claim 1, wherein thedevice includes supports, by means of which the two components are heldimmoveably in the radial direction.
 9. Device as claimed in claim 1,wherein the aligned components of the lance are oblong components. 10.Device as claims in claim 1, wherein the fitting parts are cams and thehollow profile is a hollow camshaft.
 11. Apparatus for connecting atleast one hollow part to a hollow profile shaft, compromising: a lanceassembly insertable into the hollow profile shaft and including an axialborehole operable to communicate high pressure fluid to a section of thehollow profile shaft to plastically expand the hollow profile shaft toform a press fit with a hollow part surrounding the hollow profileshaft, and seal devices on the lance assembly operable to seal off anannular space which in use forms a high pressure space for expanding thehollow profile shaft, wherein the lance assembly includes two separatealigned lance components, said axial borehole extending in at least oneof the lance components, said two lance components being spaced from oneanother to form a radial cross-flow passage from the axial borehole tothe high pressure space intermediate facing ends of the lancecomponents.
 12. Apparatus according to claim 11, wherein said sealdevices include respective ring seals on each of said lance components.13. Apparatus according to claim 11, comprising lance drive unitsoperable to selectively move the lance components to a plurality ofpositions along the length of the hollow profile shaft to therebyaccommodate sequential connection of plural hollow parts at differentaxial positions on the hollow profile shaft.
 14. Apparatus according toclaim 12, comprising lance drive units operable to selectively move thelance components to a plurality of positions along the length of thehollow profile shaft to thereby accommodate sequential connection ofplural hollow parts at different axial positions on the hollow profileshaft.
 15. Apparatus according to claim 11, wherein said hollow profileshaft is a combustion engine camshaft and each of said at least onehollow parts is a cam.
 16. Apparatus according to claim 13, wherein saidhollow profile shaft is a combustion engine camshaft and each of said atleast one hollow parts is a cam.
 17. Apparatus according to claim 11,wherein portions of said axial borehole are disposed in both of thelance components.
 18. A method of making a combustion engine camshaftassembly comprising: providing a plurality of hollow cam members withrespective cam member through passages, inserting a hollow camshaftthrough the cam member through passage and positioning the cam membersat predetermined positions spaced from one another along the hollowcamshaft, said hollow camshaft has respective first and secondoppositely facing ends, inserting a first lance component into thehollow camshaft from the first end thereof, inserting a second lancecomponent into the hollow camshaft from the second end thereof, saidfirst and second lance components exhibiting facing ends which form afirst high pressure fluid passage space applying high pressure fluid tothe first high pressure space by way of an axial borehole in at leastone of the lance components to locally expand the hollow camshaft toform a pressure fit with a first said hollow cam member, moving thelance components to different axial positions in the hollow camshaft toform a second high pressure fluid passage space, and applying highpressure fluid to the second high pressure fluid passage space by way ofthe axial borehole, to locally expand the hollow camshaft to form apressure fit with a second of said hollow cam members.
 19. A methodaccording to claim 18, wherein each lance component carries a sealingfor sealing the respective high pressure spaces with respect to annularspaces between the lance components and the hollow camshaft.
 20. Amethod according to claim 19, wherein portions of said axial boreholeare disposed in both of the lance components.